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Interventional vs Surgical Orthopedics for Stem Cell Knee ACL Repair

POSTED ON IN ACL Procedure Outcomes Knee Latest News Ligament/tendon BY Chris Centeno

I love LinkedIn as a platform for physicians to debate various issues back and forth, especially in this emerging field of regenerative orthopedic care and interventional versus surgical orthopedics. One of the things that came up this week is that while we invented and continue to publish on the ACL stem cell injection procedure that uses precise fluoroscopy placement of cells, some surgeons have been performing a bone marrow stem cell injection using arthroscopy. Is this taking too much risk if an injection can do the same thing? Let’s look at this issue in more detail.

What Is Interventional Orthopedics?

Interventional orthopedics is using precise image-guided injections of things that can help repair tissue. To learn more about the differences between interventional and surgical orthopedics, see my video below:

Our ACL Stem Cell Injection Technique

We’ve been treating ACL tears with stem cells for longer than anyone else on earth and perfected the fluoro-guided procedure. Regrettably, while mild tears can be injected with ultrasound imaging, more severe tears require fluoroscopy. See my video below on that topic:

We are able to show MRI evidence of healing and excellent long-term outcomes in select ACL tears that represent about 70% of the cases that get operated on today. See the before and after MRI results compilation that I have put together below:

Arthroscopy vs. an Injection

Knee arthroscopy is when a surgeon uses a device that can see into the knee. This has become the standard way of treating knee issues that don’t respond to physical therapy. However, the research showing that most of these arthroscopic procedures work is usually lacking, and we have copious research showing that oftentimes these surgeries are no better than placebo procedures.

The controversy on LinkedIn was that since a surgeon doesn’t usually possess the skill set or fluoroscopy equipment to perform a precise and complex injection of an ACL, should he or she perform the injection procedure with arthroscopic surgery? The main issue is the difference in risk between an arthroscopic surgery versus a precise injection using a 25-gauge needle. Meaning, in this scenario, we are using either noninvasive fluoroscopy to “see” where the needle is injecting or a surgery to open a window to “see.”

You don’t have to be an expert to see that the procedure on the left (an ACL injection using fluoroscopy) is far less invasive than the procedure on the right (knee arthroscopy).

While it would seem that there is prima facie evidence that an injection is less invasive and should carry a much lower complication profile than knee surgery, my surgical colleagues on LinkedIn were not convinced. So let’s start to dive into some research after a quick tour through surgical underreporting of complications.

My Experience with Surgical Underreporting of Complications

One of the problems with reviewing the literature for orthopedic surgical complications is underreporting. Meaning, I have seen countless complications of knee arthroscopy and other orthopedic surgeries where the treating surgeon never recognized the issue. This has spanned the gamut from mild nuisance nerve injuries leaving the patient with no sensation in a small area to serious biomechanical calamities that caused life-changing disability. Hence, IMHO, this is likely why in the below review, you will see a huge 800% spread in the reported complications for knee arthroscopy.

What Does the Research Say About Knee Arthroscopy Complications?

The possible complications of arthroscopic knee surgery include infection; nerve injury; new biomechanical problems, like instability; surgical failure; and serious blood clots. The problem with an infection acquired in a hospital, where knee surgery is often performed, versus an outpatient clinic, where a knee ACL injection is performed, is that an infection acquired in a hospital is more likely to be an antibiotic-resistant strain that’s more difficult to treat (like MRSA). This was highlighted in many news reports a few years back about infection outbreaks tied to orthopedic surgical instruments.

Overall knee arthroscopy reported complication rates vary between 1–8% (1 in 100 to 1 in 12 surgeries). Yep, that review of many papers on arthroscopic complications really has that big a range in the reporting of complications. How is that possible? See above.

In one large Swedish registry study, the rate was a little more than 1 in 100. However, this recent study reported a complication rate that was nearly 5 times higher (4.7%). On the other hand, another study found a dramatically lower serious infection rate at between 1 in 200 and 1 in 100 surgeries. Again, the reported rates are all over the place.

So what’s the real rate of knee arthroscopy complications? If we pick the middle number, likely 1 in 30 to 1 in 50 patients will have a serious complication. Now let’s look at the complication rates due to knee stem cell injections.

Knee Stem Cell Injection Complication Rates

Regrettably, there isn’t yet a large number of big studies reporting complication rates on knee stem cell injection procedures. In fact, we’re the only group on earth at this point that has meticulously tracked these events over nearly a decade and then required a physician to adjudicate them. This effort produced the world’s largest peer-reviewed study on stem cell injection complications used to treat orthopedic conditions. Click on the thumbnail below to see that study:

The highest serious complication rate that was connected to any stem cell injection procedure was 0.43% (13 possibly related complications divided by 2994 procedures). This was for culture-expanded stem cells, fat grafts, and bone marrow concentrate (BMC). The complication rate of the BMC cases was much lower at only 57% of the above number or 0.25%. Realize that even this number is likely inflated relative to the surgical cases above, as this was reported by patients and independently adjudicated by a physician as possibly or probably related, whereas all of the surgical data above is reported by surgeons who felt their complications were probably related. Meaning our data set includes complications that are likely unrelated and is likely overreporting, and the surgical data is more likely to underreport.

While all of the data above was for all types of BMC injections, what’s the actual rate in the three ACL stem cell injection data sets that we have published, submitted for publication, or are part of an ongoing RCT? That would be zero to date. However, that patient number is only about 100 cases. Hence, it’s likely that the real complication rate is somewhere between the above number and zero.

The Other Intangibles Not Being Discussed

Last year and earlier this year, we again played around with a smaller-format arthroscope. I say again because we had done this several years ago in 2012. In all of those cases, we eventually couldn’t come up with a reason why this was needed to inject ACLs when we could already do it so well using a noninvasive imaging method, like fluoroscopy. However, despite that choice, a scary revelation occurred when we realized what our surgical colleagues do when surgically treating the knee.

You see, when you stick an arthroscope in to look around, you can encounter fat pads near the patella and near the ACL. These can be “in the way,” so they are often resected with one of the arthroscopic tools to improve the view. However, we now know that these fat pads are critical reservoirs of stem cells for the joint. So the intangible here is that if in using arthroscopy you have to remove critical parts of the joint that contain the self-repair mechanism, the risk matrix for the procedure just went way up.

An ACL Injection with Stem Cells Is Far Safer than a Knee Arthroscopic Injection

No matter how you look at it, an injection with a 25-gauge needle with a noninvasive way to see the needle will always be safer than knee surgery used to see the needle. That’s not only based on easy-to-see evidence (like the comparison of what gets shoved in the knee above) but also based on the research we have available. I don’t expect that will change.

The upshot? This is one of the core tenets of interventional orthopedics as a new medical specialty: we can do it less invasively, better, and cheaper than the surgeons and help patients avoid more-invasive procedures. So should surgeons begin retraining? I think the science and the math argues that they should.

    *DISCLAIMER: Like all medical procedures, Regenexx® Procedures have a success and failure rate. Patient reviews and testimonials on this site should not be interpreted as a statement on the effectiveness of our treatments for anyone else.
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    Rick says

    Can this procedure help Meniscus tears?


    Regenexx Team says

    Yes, we treat meniscus tears regularly. Importantly, the other option, meniscus surgery has been proven not to be effective, and generally leads to arthritis. Please see: and and and


    David Greenstein OD MS says

    What is the potential for your stem cell technique for hip problems?
    I have thin cartilage in one hip that has been painful for more than 2 years.
    A cortisone injection helped for only one day after which the pain was as
    bad or worse than before the injection.


    Chris Centeno says

    David, cortisone kills cartilage, so these injections are now contraindicated based on the peer-reviewed research. I would need to see your MRI and take a history to give you a sense of how you might or might not respond.


    Phil Graf says

    I made, then cancelled an appointment with your San Rafael, California office, regarding shoulder surgery vs stem cell therapy. I cancelled because of concerns that it seems unlikely that in a bone-on-bone situation with significant wear and virtually no cushioning, stem cell therapy could be effective; and because previous shoulder replacement surgery on the other shoulder has been very successful and remarkably pain free. Looking at this article, I wonder if I should re-assess my decision to cancel?


    Chris Centeno says

    Phil, while some joints with severe arthritis like hips don't do well, severe shoulder arthritis with significant rotator cuff involvement has a higher success rate. The effect is not from regrowing a new shoulder joint with cartilage, but more likely from helping the small tears in the painful rotator cuff to heal.


    Carol says

    How does it work for a post acl repair with some acl laxity or loosening but still intact 18 months post op?


    Regenexx Team says

    We treat patients post ACL surgery. If you'd like to see if we can help in your particular case, please submit the Candidate form to the right of the Blog, or let us know and we can have someone assist with the process.


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    About the Author

    Chris Centeno

    Christopher J. Centeno, M.D. is an international expert and specialist in regenerative medicine and the clinical use of mesenchymal stem cells in orthopedics. He is board certified in physical medicine as well as rehabilitation and in pain management through The American Board of Physical Medicine and Rehabilitation.…

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